1. Field of the Invention
This invention relates to a seat back with an adjustable support and in the preferred embodiment provides a seat back suitable for use in a vehicle seat in which the adjustable support is in the lumbar region.
2. The Prior Art
Within the automotive industry considerable effort has been expended in recent years in the improvement of the comfort of vehicle seats. Particular attention has been paid to providing support for the lower back (usually referred to as the "lumbar region") of the user. With a view to accommodating the requirements of a wide range of potential users of the vehicle seat, it has proved to be desirable to provide for adjustable lumbar support.
Adjustable lumbar supports presently available either involve the use of a selectively inflatable bladder incorporated within the seat back, or involve the use of some mechanical adjustment which is effective to thrust the seat back forward (i.e. towards the user) when firmer lumbar support is required. Although the systems utilizing inflatable bladders have been found to be very satisfactory, they are relatively expensive to provide and their use tends to be limited to relatively expensive vehicles. Existing mechanically adjustable lumbar supports which would be acceptable on a cost basis for less expensive vehicles are, however, less than satisfactory. In particular, in such designs some form of rigid bar or plate spans the width of the back support in the lumbar region. Increasing the degree of lumbar support thrusts this bar or plate forward, and whilst this does increase the pressure applied to the back of the user of the seat, the presence of an essentially rigid bar or plate has been found to be uncomfortable by users of the seat when the system is adjusted to provide a substantial degree of lumbar support.
The present invention provides a mechanically adjustable lumbar support which can be manufactured economically and which does not involve the use of any rigid bar or plate which is thrust forward to increase the degree of lumbar support provided by the seat.